Embodiments of the invention relate to a method and apparatus for treating a malfunctioning dosing valve of a dosing device.
A dosing system is known to reduce mono-nitrogen oxides NO and NO2 (nitric oxide and nitrogen dioxide) output from an exhaust pipe connected to an internal combustion engine of a vehicle. A DNOx sensor senses a concentration of nitrogen oxides NOx in an exhaust pipe and a dosing valve sprays urea solution, such as diesel emission fluid (DEF), into the exhaust pipe connected to the internal combustion engine of a diesel vehicle. This technique, as part of a selective catalytic reduction system (SCR), significantly reduces residual nitrogen oxides output in the exhaust of the vehicle.
FIG. 1 shows a known dosing system 20 for an internal combustion engine that includes an electronic dosing device controller 24 that provides electrical power over an electrical connector 26 to a dosing device 30. The electrical power controls a dosing valve 34 of the dosing device 30. FIG. 1 also shows a urea solution storage device 38 and a fluid connecting line 40 joined by a fluid connector 44 to a first end 46 of the dosing device 30. A second end 48 of the dosing device is in communication with an exhaust pipe 50.
The dosing device 30 includes a dosing valve 34 having a dosing valve needle that is controlled to spray urea solution into the exhaust pipe of a diesel vehicle. In some instances, crystals are formed in the dosing device 30 due to an insufficient purge of the urea solution about the dosing valve needle or due to lack of use or actuation of the dosing valve needle for a long period of time. In instances wherein the dosing valve 34 is inoperative, the dosing device 30 is entirely removed from the vehicle and replaced.
FIG. 2 shows a dosing valve 34 that includes a connector member 54 and an electrical terminal 56 for joining to the electrical connector 26. The dosing device 30 includes various elements of a dosing valve, including an extension tube 58, a basket filter 60 and an adjustment sleeve 62. Further, the dosing valve 34 includes a spring 66 and a support tube 68 disposed within the extension tube 58. Further, the dosing valve 34 includes a needle sleeve 70 for surrounding the dosing valve needle. The dosing valve 34 includes a valve ball 74, a valve seat 76 and an orifice plate 80.
The dosing valve 34 shown in FIG. 2 includes a magnetic coil or bobbin 84 that receives electrical power and acts as an actuator to move the dosing valve needle that acts as a dosing valve. Further, FIG. 2 shows a housing 86, a grommet 88, an armature 90 and a cover 92 of the dosing valve 34. The dosing valve needle moves axially in operation to spray urea solution into the interior of an exhaust pipe.
One object of the invention is to treat a dosing device so that the dosing valve operates properly without requiring removal and replacement of the dosing device from a vehicle.